The Commonwealth was the republican government which ruled first England and then the whole of Britain and Ireland during 1649 - 1653 and 1659 - 1660. The term is also loosely used to describe the system of government during the whole of 1649 - 1660, the years of the Interregnum[?], although during 1653 - 1659, the government is properly called The Protectorate and took the form of direct personal rule by Oliver Cromwell, the Lord Protector.
... refer to a thing which is not specified in any of the parts of which the compound is formed. A block-head, for example, is someone whose head is said to be as thick ...